The molluscan bivalve exoskeleton and mantle epithelium have been chosen for structural, chemical and physiological studies to determine factors leading to biomineralization. The hinge ligament is particularly suited to chemical and ultrastructural studies. The outer mantle epithelium, which maintains a bidirectional flux of calcium, has been selected for calcium transport studies. Pectinidae hinge ligament contains both a calcified and a noncalcified region. In addition to the matrix elastomer both zones contain an extensive sheet-like network. In the calcified zone this network contains the mineral. The sheet networks in both zones are structurally similar but cytochemically distinct. We propose that the noncalcified network is a precursor to the calcified network. The sheet networks will be isolated by use of denaturing agents and disulfide bond reductants or by preferential proteolysis of the matrix elastomer. The isolated sheet networks will be analyzed and the analyses compared to determine if the sheet works are compositionally similar, thereby establishing a precursor-product relationship between them. At the same time we will be seeking a specific chemical alteration in the calcified network, which renders it calcifiable. Its identification is a major goal of this project. In the matrix elastomer of the scallop ligament 2/3 of the amino acid residues are glycine. The elastomer will be analyzed for the presence of polyglycine by digestion of the elastomer. The resulting fragments will be isolated and amino acid compositions determined. Sequence analyses will be performed if necessary. We propose that elastic properties of the ligament are related to transformation between a polyglycine I and a polyglycine II-type structure. Isolation and chemical analyses of intercellular granules found in the mantle epithelium will be performed. These granules have been proposed to be calcium rich and to function in the transport of calcium via intercellular pathways. Ion flux measurements will be initiated to determine the extent of intracellular transport and cellular control of calcium movement. These studies will be done in vitro using Rangia cuneata.